Energy consumed by humanity is limited, and global warming due to carbon dioxide generated as a result of the consumption of the limited energy is the biggest problem which humanity has along with the energy crisis. Accordingly, energy regulations of each country are being strengthened day by day, and an energy rating system for household appliances is a permanent assignment which manufacturers face. Information of the energy rating system requiring maximum efficiency with less energy is in good agreement with the needs of consumers who require a high appropriate content amount and low power consumption. In particular, a lot of research on refrigerators has been conducted over the past several decades, and research on efficiency improvement for a cooling cycle, a compressor, a heat exchanger, and the like has already reached its limit. Accordingly, in recent years, research on heat loss has been mainly conducted, and a lot of attempts have been made to increase energy efficiency by enhancing insulating performance of refrigerators.
An existing heat insulating material such as polyurethane has a thermal conductivity of about 20 mK/m·K, and when using this, the thickness of an outer wall of a refrigerator is increased, resulting in a reduction of the storage capacity of the refrigerator. Accordingly, the use of a vacuum insulation panel having excellent heat insulating performance is required in order to solve this problem.
However, a heat bridge phenomenon (a phenomenon in which heat flows through edges of the vacuum insulation panel) and durability of the vacuum insulation panel are in conflict with each other, and therefore there is a limit in efficiently manufacturing the vacuum insulation panel.